Process for forging hollow tubular objects



Jan. 22, 1957 A. E. DULLUM 2,778,101

PROCESS FOR FORGING HOLLOW TUBULAR OBJECTS Filed Aug. 5, 1952 3 Shee ts-Sheet 1 PROCESS FOR FORGING HOLLOW TUBULAR OBJECTS Filed Aug. 5, 1952 A. E. DULLUM Jan. 22, 1957 3 Sheets-Sheet 2 m 5! ma 0 5 m a r A Z 6 i, 4 e J U U HH I n 4% v w Fwlllliu NU. Wu HM f n 4 4 ATTORNEYS.

Jan. 22, 1957 A. E. DULLUM 2,778,101

' PROCESS FOR FORGING HOLLOW TUBULAR OBJECTS Filed Aug. 5, 1952 3 Sheets-Sheet 3 INVENTOR Arffiwr 1 fiulfam United States Patent 2,778,101 p tented Jan, 22, 1957 ice condense with the n e t o P rtly in sss iq en the x s t th i a f h tu ntab e e sea in ing a en on the line 171 of Figl m 2. 2, ,101 Fig re ,2 s. a p an cti at Fi ure 1 on th i Z- PROCESS FOR FORGING HOLLOW TUBULAR 5 F gu e. 3 is a p an iew of he gripping machine of Figr OBJEcTS ures 1 and 2.

Arthur E- Du m, Jerse City, N-

Application August 5, 1952, Serial No. 302,798 1. l im- (c -2 55.

h present n n i r ate t0 forgin rm s and toy processes of forging hollow tubular articles such as artillery shells.

A purpose of the invention is to forge hollow tubular articles more closely to size, thus, saving machining, for example, by eliminating draft on the die and punch:

A further purpose is to improve the cpncentricity of hollow tubular forging articles by separating the die beo h la is ns ed, n e in the b ank b ngi e opp ed e a e her a d d ft; '1 s the ank at h ne t p it thaut fu l f r .1a the blan to fi the e cavity, p r ng e b n by the bun h whi e thus gripped, thus minimizing forward movement of the me al. a i t ui e om a e l m v ment dur n Pier g. Wit dra in th p nch, nd paratin he die ha ves- A t er pu p i to bt in impro ed. M o o ss me al n forming ho a ubul ar i l s such a s el by gripping the blank at the corners to prevent buckling during piercing.

A further purpose is to eliminate excess stock and thus reduce the need for machining.

A further purpose is to lower tool costs by making it possible to form the die and refinish the die from an open side without using die sinking methods, and readjnst'the position of the die halves to close the die after the meld has been reconditioned.

A further purpose is to avoid the need for expensive upsetting equipment in forging hollow tubular objects.

A further purpose is to make it easier to unload the die in forming shells and the like.

A further purpose is to insert a polygonal blank in separated halves of a die, to laterally form the blank at the corners in closing the die, and to thus support the blank during piercing and until after the punch has been withdrawn.

A further purpose is to guide the punch in all four lateral directions immediately before it enters the blank and so long as it is entering the blank.

A further purposeis to holdthe die halves together by a toggle lever and adjust the toggle lever olosing position as the die half positions change with wear and reconditioning of the dies.

A further purpose is to cool the punch between each complete cycle of operations on a particular blank by moving the punch on a turntable to' a cooling position.

A further purpose is to. obtain better working of the metal of the blank in a few. steps, permissibly with rest between forging steps as required.

A further purpose is to improve the safety of the forging operation.

Further purposes appear in the specification. and in the claim.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in whichmyinvention-may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactoryoperatioh and clear demonstration of the principles involvem' Figure l is a side elevation Ora forging pres i Figure 4 is a vertical section on the line 44 of Figure 3, omitting the part of the, guiding structure for the punch, and showing the die halves closed.

Figure 5 is a view similar to Figure .4, with the die halves open, and with part of the support and hydraulic c inder b oke away.

Figure 6 is a right end elevation of Figure 3, with the bed broken away.

Figures 7 to 11 are fragmentary diagrammatic views Showing the g f i in accordance w h he e io Figure 7 being a top plan with the die halves open and the blank inserted, while Figure 8 is a section of Figure 7 on the line 8--8.

Figure 9 is a plan view with the die halves closed before piercing. l

Figure 10 is a plan section showing piercing.

Figure 11 is a'plan view showing the die halves sepa rated and the finished forging ready for removal from the dies. 4 i

In the prior art comparatively heavy forgings of hollow tubular form such as artillery shells from millimeters up have been difficult and expensive to forge by any of the accepted methods, such as the upsetting method or the pierce and draw method.

The tendency in the prior practice has been to require excessive machining, due to the inability to forge precisely to dimensions. This has been partly caused by variations in eccentricity due to forcing a considerable amount of metal forward during piercing under conditions. in which the flow is slightly uneven on different sides of the shell, due to the presence of excess stock which must be machined away, and due to the tapering of the outside diameters due to the requirements of a draw angle to remove the shell from the die. One of the important advantages of the present invention is that hollow tubular objects such as shells can be forged substantially to size, eliminating a great deal of unnecessary machining. The concentricity is improved by the present invention because the blank does not move forward appreciably during piercing, but is gripped in a forward position. Flash is largely eliminated, and, since no draw angle is needed for the purpose of extracting, machining to eliminate taper due to draw angle is avoided.

The tooling cost has been high in prior art practice, not only due to the necessity of using relatively expensive methods of maehining such as die sinking in making the die but also because the life of the dies is comparatively li rnted. In aceordance with the present invention, die halves are accessible laterally for machining by ordinary methods at moderate cost. As the die wears, the cavity a c be u aw y t make a. ace, and the mating surface of the die half is correspondingly cut away. Thus the half can progressively change its position as wear and erou it Qu uaqqwh Under prior art forging methods there was a tendency ter or sts-de e tive tqrs sduc to buc l during pi ing' or squeezing of the. steelto fill the cavity as the punch n e sat ordansew th the pres nt; in en i n he b n is gripped and d fe s at the ea n r e P c n nd. the r pp ng p ev t he ms b l y of in spiersitteandhisdus at d s in h fam lie The gripping pressure desirably re ai until after the punch switl dramm ta sta ed and his perm s. i th die 91 a ree w king of 3 the metal is obtained in afew steps, and it is seldom necessary to reheat during forging.

Part of the difliculty in the prior art has been due to the tendency of the punch when it encounters unequal resistance to deflect slightly to one side. In accordance with the present invention, guiding surfaces on the die engage guiding surfaces on the punch before the punch enters the die or encounters the blank, so that the likelihood of any deflection of the punch is greatly reduced.

No possibility exists in the present invention of momentary parting of the die halves which could cause flash, since the die halves are locked by a toggle lever, and the toggle lever position is adjustable to allow for wear and reconditioning of the die halves.

The present invention avoids the necessity of using any expensive upsetting equipment as required in the prior art.

In accordance with the present invention any desired rest periods can be provided between the increments of forgings to work the metal in the most favorable manner.

The device of the invention is very safe from the operators standpoint, since the die halves are separated at the beginning when the blank is inserted and also at the end of the cycle when the blank is removed.

The invention lends itself well to cooling of the punch by inserting it in a cooling bath between punching operations.

Considering now the structure shown in the drawings, a suitable hydraulic press has a bed 21, a head 22 and interconnecting tension and guiding rods 23.

A main ram 24 operates in a main cylinder 25 to manipulate a movable platen 26 which is suitably guided on the rods 23.

The platen 26 carries on the axis of one of the guiding rods 23 a bearing 27 which pivotally mounts a turntable 28 which is guided at its outer ends by an annular track 3t supported at one side by the platen proper and at the other side by brackets 31 secured to the platen.

The turntable is manipulated by a motor 32 driving a gear 33 which intergears with the turntable in a gear path 34.

The turntable has at four stations thereon suitable rectangular punch holders 35 which support punches 36 and 37 which are designed for progressive work on the same blank to take it through the various stages of forging. While two punches are shown, it will be understood that any suitable number may be employed in each set.

The punch holder 35 is suitably rectangular and has lateral guiding surfaces 38 which are adapted to cooperate with guides on the die as later explained.

The bed of the press at 21 supports a bed extension 40 on which is mounted the under frame 41 of a gripping machine 42.

The gripping machine has a side frame 43 consisting of spaced supports, which is interconnected to the under frame 41 at the bottom, and is cross connected by a stationary die holder 44 and a spaced crosshead buttress 45. The stationary die holder 44 is braced against yielding away from the crosshead buttress by bracing blocks 46 secured to the under frame and in the case of the blocks adjoining the side frame keyed at 47 (Figure 6) to the side frame. Likewise the crosshead buttress is backed up by supporting blocks 48 which are similarly held in position.

The stationary die holder has a suitably rectangular recess 50 which receives a stationary die half 51 which is held in position in the stationary die holder by keys 52.

A cooperating movable die half 52 is mounted in a die receiving recess 53 of a movable die holder 54 by keying at 55. Suitable shims 56 are introduced at the ends to line up the bottom die with the punch.

The movable die holder 54 is guided at the bottom at 57 on the under frame 41, and has journal extensions 58 away from the stationary die holder. The movable die holder 54 engages at the sides in laterally extending guide tracks 60, suitably located at the top, bottom and middle of the side frames 43.

A pivot pin 61 extends across between the journal extensions 58 and pivotally interconnects with toggle levers 62 which in turn at their ends remote from the die pivotally interconnect through pin 63 with a crosshead 64 having a pivoting lug 65 through which the pin 63 extends. The crosshead 64 has, as best seen in Figure 3, guiding side extensions 66 which are received and guided by guideways 67 on the crosshead bolster 45.

The crosshead is manipulated up and down by a piston 68 having a piston rod 70 which is adjustably connected by a thread at 71 with the crosshead and has a lock nut 72 to secure the piston rod in the proper adjusted position. The piston is operated in a double action hydraulic cylinder 73, suitably under the action of any desired hydraulic medium such as water or oil.

The die halves extend above the die to form rectangular guiding surfaces 74, best seen in Figure 3, which engage the guiding surfaces 38 on the punch before the punch enters either of the tool cavities 75 of the die.

Each of the tool cavities 75 i suitably tubular, and

its walls are desirably formed without any draw angle.

Any suitable nose construction will be provided in the die cavity 75 of the die as indicated at 76.

The forging operation will preferably be performed in steps, first forging die cavity 77 and the punch 36 producing a forging 78 as shown in Figure l, and a second forging die cavity 80 and the punch 37 producing a forging 81 as shown in Figure 1.

As the punch is likely to be heated somewhat rapidly it is desirable to increase tool life by cooling the punches. When the platen 26 retracts to its upper position, therefore, the motor 32 is operated manually or automatically as desired to turn the turntable to bring the punches which have just been employed in forging to a position above the suitably curved cooling tank 82 (Figures 1 and 2), to be cooled by Water or other suitable cooling medium 83 circulated as required to keep down the -tem-.

perature and replenish the cooling medium. The cooling tank is supported on brackets 84.

The operation of forging in accordance with the present invention is best understood by reference to Figures 7 to 11 inclusive. At the position of Figures 7 and 8, the die halves 51 and 52 are separated (although not necessarily at the position of widest separation), suitably by moving the crosshead toward the position of Figure 5.

' A blank 85 at forging temperature, consisting of steel or any other suitable metal, and of polygonal form (here shown as rectangular, but permissibly pentagonal, hexagonal, octagonal, etc.) is inserted from above into the space of the forging cavity 75 of the die. No deformation of the blank occurs in inserting the blank.

Next hydraulic fluid is applied to the end of the cylinder 73 to force the piston 68 down in Figure 4 and close the die halves as shown in Figure 9. This causes the corners of the blank to be deformed at 86 and gripped by the die halves, but the mold is still not completely filled as seen by the existence of spaces 87 between the blank and the mold, so that there is no tendency by this operation to force the metal out into the space 88 (Figure 7) between the closing mold halves, which would prevent the mold halves from fully closing and form flash.

In the next operation as shown in Figure 10, the punch moves down, the surfaces 38 on all four sides of the punch first coming into guiding relation with the surf-aces 74 on all four sides of the guide portion of the die. Then the punch 36 enters the blank and pierces it as seen in Figure 10, accomplishing the forging operation proper. All of this time and until after the punch has been withdrawn from the forging, the toggle levers are set or locked in straight line relation between the pivots 61 and 63 of Figure 4 and the die, so as to prevent any separation of the die halves.

Next the hydraulic pressure is applied to the end of the piston 68 remote from the crosshead, causing the mold halves to separate as shown in Figure 11, so that the finished hollow tubular forging 78 is ready for removal from the dies. Access for removal purposes is easy, since the space 88 permits the insertion of tongs or the like on the sides of the forging. The forging can thus readily be shifted from one die cavity to another as the work progresses and can eventually be wholly removed.

It will thus be seen that in the operation as just described the blank as inserted in Figure 7 is too large to permit the die halves to come together without deforming and gripping the blank at the corners, but it is too small to wholly fill the mold when the die halves come together, so that there is no tendency to squeeze metal out and form flash. The gripping pressure is applied before the vertical stroke which causes piercing, and the blank before the vertical stroke is well seated in the die cavity and does not have to move forward appreciably. There is thus no possibility of buckling or squeezing of the steel which might form a fold line or similar defect. Since the blank is not moving forward appreciably during pressing and since the punch is guided in all four directions during piercing, the previous difliculty with lack of concentric-ity in the forging is avoided.

Likewise since the mold halves are separated at the time the forging is withdrawn from the mold, the forging machine is very easy to unload, and no draw angle is required to aid in ejecting.

It is important now to consider the action taken in the ease of wear of the dies. The die halves protrude toward one another at 90 as shown in Figures 3, 4 and 5 beyond the die holders, and there is substantial excess metal which can be used to refinish the dies. To acoomplish this purpose the dies are removed and the curved surfaces 91 (Figure 11) are machined away a minute amount as suggested by the dotted line, and a corresponding minute cut is taken on the mating surfaces 92 as suggested by the dotted line (Figure 11). Of course it will be understood that the wear on these surfaces may be different and this will be compensated for in machining. Then the reconditioned dies are reinserted in the die holders, the key positions being unchanged, and adjustment is made at the thread 71 and the lock nut 72 so that the toggle will be straight and locked when the dies are tightly closed. This readily compensates for required refinishing of tooling, and at low cost since both a side and an end of 'the die half are accessible for machining.

During the forging operation, each time the piston moves up after completion of forging by a particular set of punches, the punches are changed and the punches just used are subjected to cooling by the cooling medium 183 for the time required for three subsequent forging machine of the invention will operate under a press of any desired tonnage, although it will be evident that in every case the gripping pressure will be greater than the vertical forming pressure of the press. The gripping machine is also capable of movement to any location on the base of the press to line up with the particular punches.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the process and structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claim.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

The method of forging a hollow tubular metallic object, using separable die halves which together form a cylindrical die cavity, which comprises placing between the die halves aheated polygonal blank whose corners extend out far enough to be gripped by the cylindrical walls of the die cavity when the die is closed but whose cross section is insuflicient to fill the die cavity with metal of the blank when the die is thus closed, closing the die halves and thus squeezing the polygonal blank to grip the same by lateral engagement of the walls of the die cavity against the blank and at the same time deforming the blank at the corners While leaving free space between the blank and the cylindrical interior Walls of the die at some points so there is not a tendency to force out metal of the blank and form a flash between the die halves, partially piercing the cavity in the blank but leaving unpierced blank material at the forward end while thus gripping the initial free lateral space at points around the blank and thereby forcing the material of the blank out into engagement with the interior cylindrical walls of the die throughout the circumference, releasing the interior piercing pressure on the blank, then releasing the lateral gripping pressure on the blank by separating the die halves, gripping the blank in a further cylindrical die cavity by bringing die halves together, simultaneously further piercing the blank and deforming the previously pierced portion to thin the wall and form the desired cylindrical shape, releasing the interior piercing pressure on the blank and then releasing the lateral gripping pressure on the blank by separating the die halves.

References Cited in the file of this patent UNITED STATES PATENTS 495,245 Ehrhardt Apr. 11, 1893 717,886 Mercader Jan. 6, 1903 761,778 Mercader June 7, 1904 1,251,128 Steedman Dec. 25, 1917 1,286,687 McGary Dec. 3, 1918 1,633,970 Ball June 28, 1927 2,106,830 Criley Feb. 1, 1938 2,215,943 Traut Sept. 24, 1940 2,261,304 Sparks Nov. 4, 1941 2,299,105 Muir Oct. 20, 1942 2,343,403 Criley Mar. 7, 1944 2,451,512 Rice Oct. 19, 1948 2,647,421 Criley Aug. 4, 1953 

